Methods and systems for providing limited data connectivity

ABSTRACT

In one embodiment, a system, apparatus, and method are described for providing limited data connectivity for devices connected to a switch when the switch enters bootloader mode. The switch has a central processing unit (CPU), the CPU comprising a reload handler and an application-specific integrated circuit (ASIC), the ASIC comprising ASIC forwarding logic. The ASIC is instructed, by the reload handler, to store an ASIC database, the ASIC database for storing the ASIC forwarding logic. The reload handler maintains a physical layer (PHY) state of the switch. Use of spanning tree protocol (STP) and Transmission Control Protocol (TCP) keepalive is disabled in the switch. A state of stack hardware is retained in switch memory. New ports of the switch are prevented from becoming active, and the ASIC forwarding logic is, in response to receiving the instruction, stored in the ASIC database. Related systems, apparatuses, and methods are also described.

TECHNICAL FIELD

The present disclosure generally relates to power over Ethernet systems.

BACKGROUND

Persistent power-over-Ethernet (PoE) has solved one of the majorproblems in connected lighting. Power is delivered during maintenancereload for power critical devices, e.g. ceiling lights. PoE powereddevices requiring power persistence are not limited to just lightingdevices. However, even with Persistent PoE, during the maintenancereload, the management plane has no control over the PoE devices sincethere is no end-to-end data connectivity, and thus, no input from thePoE devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be understood and appreciated more fullyfrom the following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a block diagram illustration of a first embodiment,constructed and operative in accordance with an embodiment of thepresent disclosure;

FIG. 2 is a block diagram illustration of a second embodiment,constructed and operative in accordance with an embodiment of thepresent disclosure;

FIG. 3 is a block diagram illustration of a third embodiment,constructed and operative in accordance with an embodiment of thepresent disclosure;

FIG. 4 is a block diagram illustration of a fourth embodiment,constructed and operative in accordance with an embodiment of thepresent disclosure;

FIG. 5 is a block diagram illustration of a fifth embodiment,constructed and operative in accordance with an embodiment of thepresent disclosure;

FIG. 6 is a block diagram illustration of a generalized embodiment,constructed and operative in accordance with an embodiment of thepresent disclosure; and

FIG. 7 is a flow chart of a method of operation for one embodiment ofthe present disclosure.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

In one embodiment, a system, apparatus, and method are described forproviding limited data connectivity for devices connected to a switchwhen the switch enters bootloader mode. The switch has a centralprocessing unit (CPU), the CPU comprising a reload handler and anapplication-specific integrated circuit (ASIC), the ASIC comprising ASICforwarding logic. The ASIC is instructed, by the reload handler, tostore an ASIC database for storing the ASIC forwarding logic. The reloadhandler maintains a physical layer (PHY) state of the switch. Use ofspanning tree protocol (STP) and Transmission Control Protocol (TCP)keepalive is disabled in the switch. A state of stack hardware isretained in switch memory. New ports of the switch are prevented frombecoming active, and the ASIC forwarding logic is, in response toreceiving the instruction, stored by the ASIC in the ASIC database.Related systems, apparatuses, and methods are also described.

EXEMPLARY EMBODIMENTS

In embodiments described herein, methods of making limited dataconnectivity available for Power-over-Ethernet (PoE) devices and non-PoEdevices during planned and unplanned system outage of variousembodiments of stackable, modular chassis, and stand-alone stitches aredescribed. Switches (such as, but not limited to Cisco switches, orother comparable network switches) typically operate in one of stackedmode or standalone mode, as well as a modular chassis system, andsupport data forwarding end-to-end for the user devices when switchsoftware has failed. Some embodiments described herein, eitherseparately or in combination, define a method of maintaining persistentnetwork connectivity when main software is not active or has failed,e.g., during a switch maintenance reload. Thus, if an entire full stackor chassis software networking system has failed, limited networkconnectivity can still be provided, as will be described below.

By way of example, the ability to make an emergency phone call using PoEtelephone devices during system failure may be provided. Other exemplaryembodiments may involve supporting critical medical monitoring systems(e.g., heart monitoring system) and building alarm systems, in order toensure that these systems maintain limited data connectivity duringswitch down time.

By way of introduction, when a switch undergoes a reload, a crash ormalfunction, a software or firmware upgrade, or is only minimallyoperational for some reason for a period of time, the switch will, asdescribed below, enter “auto-pilot” mode. In such a case, switchhardware maintains a data plane with a previous known configuration andforwarding configuration. Accordingly, minimal disruption occurs duringa transition to a new software or during a crash scenario.

The switch may comprise a stackable switch, a standalone switch, amodular switch, a modular switch with one or more supervisory modules,an enterprise switch, or other switch configurations known in the art. Areload handler, running in a central processing unit (CPU) of the switchperforms, at least, the following, in order to keep the switch in“auto-pilot”, and provide connectivity to PoE devices already connectedto the switch:

-   -   A database resident in an application-specific integrated        circuit (ASIC) disposed in the switch is retained. The database        maintains the ASIC forwarding logic, so that packets are        forwarded properly from their ingress into the switch to their        egress from the switch.    -   A physical layer (PHY, typically a dedicated chip), is retained.        That is to say the electrical and physical connections are        maintained, ensuring transmission and reception of raw bit        streams, between devices connected to the switch to an outbound        port from the switch.    -   An implementation of spanning tree protocol (STP) is disabled in        the switch.    -   Use of Transmission Control Protocol (TCP) keepalive is disabled        in the switch.    -   A state of stack hardware and software in the switch is retained        in memory by the switch.    -   No new ports may be added to or activated in the switch.

The above are referred to below as “minimal operation of the reloadhandler”.

In ordinary operation, the switch typically forwards packets via theASIC disposed in the switch. This pathway through the ASIC may bereferred to as a “fast pathway”. When the switch is in “auto-pilot”mode, the pathway is via the switch CPU and not via the ASIC. Thispathway may be referred to as slow-path forwarding, or minimum slow-pathforwarding.

Reference is now made to FIG. 1, which is a block diagram illustrationof a first embodiment constructed and operative in accordance with anembodiment of the present disclosure. FIG. 1 depicts a member reloadscenario for a partial stack down scenario in a stackable or modularchassis switch, such as stackable switch 100. The system of FIG. 1comprises at least two switches (which will be described below) whichare stacked together in a stackable switch 100. A first switch, whichfunctions as master switch 110, as is known in the art, manages thestackable switch 100, and serves as a control center for the stackableswitch 100. Typical management tasks include fault detection, virtuallocal area network (vLAN) creation and modification, security, andquality of service (QoS) controls. The stackable switch 100 has only oneconfiguration file, which is distributed to each member switch in thestackable switch 100. In some embodiments, by way of a non-limitingexample, there may be up to nine switches (i.e. the master switch, andeight member switches) in the stackable switch 100. This allows eachswitch in the stackable switch 100 to share the same network topology,media access control (MAC) address, and routing information. Inaddition, it allows for any member switch in the stackable switch 100 tobecome the master switch 110, if the master switch 110 ever fails.

A second switch, member switch 120, which is a member, i.e., anon-master, switch of the stackable switch 100 is also comprised in thesystem of FIG. 1. As noted above, there may be other member switches.

The master switch 110 and the member switch 120 comprise a centralprocessing unit (CPU) 121, 122, respectively, which provide an executionplatform for executing machine readable instructions such as software.The CPU 121, 122 comprises dedicated hardware logic circuits, in theform of an application-specific integrated circuit (ASIC), fieldprogrammable gate array (FPGA), or full-custom integrated circuit, or acombination of such devices. Alternatively or additionally, some or allof the functions of the CPU 121, 122 may be carried out by aprogrammable processor microprocessor or digital signal processor (DSP).

The CPU 121, 122 comprises a reload handler 123, also called a crashhandler, which, as will be explained below in greater detail, is invokedwhen a member reload command or a slot reload command is used to bringdown a particular switch in a data stack, or alternatively, if a memberswitch (e.g., member switch 120) needs to be reloaded due to a softwaremalfunction. The reload handler 123 is depicted in FIG. 1. However, forease of depiction, the reload handler 123 is not depicted in figures ofother embodiments, although it is understood to be comprised in the CPUdescribed in the other embodiments.

The master switch 110 and the member switch 120 comprise ASIC forwardinglogic 124, 125. The ASIC forwarding logic 124, 125 ensures that packetsare forwarded properly from connected devices, such as devices 142, 144,146, through the member switch 120 to the master switch 110 as needed.The ASIC forwarding logic 124, 125 comprises an ASIC database 126,which, as described below, stores forwarding data so that, during areload, crash, or malfunction, forwarding may be maintained to knownaddresses. For ease of depiction, the ASIC database 126 is not depictedin figures of other embodiments, although it is understood to becomprised in the ASIC described in the other embodiments.

The master switch 110 and the member switch 120 comprise a networkinterface function (NIF) 127, 128, which interfaces between the internalhardware and software of the master switch 110 or the member switch 120and the “outside world”, i.e. devices, such as devices 142, 144, 146, orother networking hardware (not depicted) to which the stackable switch100 may be connected.

The NIF 127, 128 is connected to a downlink 129, 130, through whichcommunications flow to and from those devices 142, 144, 146, or othernetworking hardware (not depicted for the master switch 110) to whichthe stackable switch 100 is connected. The NIF 127 of the master switch110 is also connected to an uplink 131, through which communicationsflow to a network 160. The network 160 might comprise an internalnetwork, an external cloud, the Internet, or a combination of internaland external networks.

Additionally, the master switch 110 and the member switch 120 comprisehardware and software (indicated as “stack” 132, 133) by which themaster switch 110 and the member switch 120 are integrated into thestackable switch 100. A stack cable 135 comprises a physical link bywhich the master switch 110 and the member switch 120 are physicallyconnected.

Turning to the operation of the system of FIG. 1, if the member switch120 has gone down and entered bootloader (sometimes referred to as“ROMmon”, i.e., ROM monitor) mode, the member switch 120 becomesinoperative. As is known in the art, by way of example, a Cisco or otherswitch may go into ROMmon mode due to boot failure. When the switchenters ROMmon mode, a virtual configuration register setting forces theswitch (such as member switch 120) to stop in ROMmon mode duringboot-up. Or, alternatively, if a break sequence is sent to a consolecontrolling the switch (such as member switch 120) during boot-up, theswitch (such as member switch 120) enters ROMmon mode.

The plurality of devices 142, 144, 146 may be configured to maintainpersistent network connections, as well as to maintain persistent PoEpower. Such devices may include an Internet Protocol (IP) telephone 142,a PoE heartbeat monitor 144, and a PoE light or alarm 146. It isappreciated that these devices are mentioned by way of example only, andany appropriate PoE device may be connected to the member switch 120.Additionally, it is appreciated that FIG. 1 depicts these PoE devicesconnected to the member switch 120. As a matter of practice, there maybe up to as many connected devices as may be supported by the memberswitch 120, or, as few as one device may be connected.

In an embodiment, when the member switch 120 enters ROMmon mode, thehardware of the member switch 120 enters “auto-pilot” mode, wherein thehardware maintains a data plane with a previous known configuration andforwarding configuration. Accordingly, minimal disruption occurs duringa transition to a new software or during a crash scenario.

A default dynamic destination index (DI) entry is programmed at the timeof the crash, reload, or malfunction, as an entry in the ASIC forwardinglogic 125 in order to reroute a data-path through the member switch 120via a stack-ASIC interface (SIF) (included in the stack 132, 133hardware and software) over the stack cable 135 to the master switch110. The master switch 110 passes packets received over the SIF from themember switch's 120 egress path to ingress forwarding logic of themaster switch 110 using a re-circulation path 150. The recirculationpath 150, as its name would suggest, recirculates the packets back tothe member switch 120. The path of the packets sent from the pluralityof devices 142, 144, 146 to the network 160 is illustrated with a dashedline 152. The return path is shown as a dotted line 154. Recirculatingthe packets to the member switch 120 ensures that communicationcontinues to the plurality of devices 142, 144, 146 is maintainedregardless of the crash, reload, or malfunction.

The master switch 110 makes no changes in how packets received in thismanner from the presently down member switch 120, are treated.Accordingly, these packets are forwarded to an appropriate destinationswitch through the SIF path, depicted as a dotted line in FIG. 1.

However, during this period, the member switch 120 will not establishany new connections, and no new PoE device will be powered by the memberswitch 120.

By way of a summary of the above discussion, a first, dotted line 154indicates “normal” path of data packets through the stackable switch 100(where the dotted line is understood to flow in both directions), and asecond, dashed line 152 indicates the upstream path of data packetsthrough the stackable switch 100 when reload handler 123 invokes minimalslow-path forwarding.

Reference is now made to FIG. 2, which is a block diagram illustrationof a second embodiment, constructed and operative in accordance with anembodiment of the present disclosure. When a complete stack reloadoccurs, and all members of the stackable switch 100, including themaster switch 110 (and any standby master switch (not depicted)), all ofthe switches in the stackable switch 100 enter ROMmon mode, i.e., theyenter boot-loader. This results in all active software in all of theswitches in stackable switch 100 being terminated. In such a case, thereload handler 123 performs the following in order to keep theconnection to the plurality of devices 142, 144, 146 up and running:

All of the actions mentioned above with reference to FIG. 1 as beingperformed are also performed on all of the members of the stackableswitch 100, including the master switch 110 (and any standby masterswitch (not depicted)).

The data-path now defaults to a management Ethernet port (MGMT) 155 ofthe master switch 110 for all look-ups in the ASIC forwarding logic 124,125 which fail due to the entry into ROMmon mode. Data from any activeswitch (e.g. member switch 120) is routed to the CPU 121 via a defaultentry in the ASIC forwarding logic 124, 125.

Forwarding for Layer 2 and Layer 3 of the Open Systems Interconnectionmodel (OSI) model to locations which were known to the stackable switch100 before the complete stack reload began continues to occur normally.

Packets from the CPU 121 use a data-path which is available to themaster switch 110 via the management Ethernet port 155.

Packets which cannot be switched through the ASIC forwarding logic 124,125 (due to being in ROMmon mode) are then “punted” to the nextswitching level (i.e., fast switching or process switching) via the CPU(i.e. via the reload handler 123). These punted packets are subjected toa proxy forwarding logic in the boot-loader (not depicted). The proxyforwarding logic modifies Layer 3 addresses from packets which arecoming from PoE powered devices (“PD devices”) and adds the IP addressof the MGMT port address as a source IP. The boot-loader creates andmaintains a table of device contexts in form of <MAC, VlanID, srcIP,MgmtIP, TargetedDestIP> for packet modification of forwarding from CPUto MGMT port and CPU to ASIC. The fields in the above mentioned aboveare as follows:

MAC—the MAC address of the device from which the packets originated.

VlanID—an identifier of the virtual LAN on which the device which thepackets originated is located.

srcIP—the source IP address from which the packets originated.

MgmtIP—the IP address of the management port through which the packetswere re-forwarded.

TargetDestIP—the IP address to which the packets are to be sent.

Reference is now made to FIG. 3, which is a which is a block diagramillustration of a third embodiment, constructed and operative inaccordance with an embodiment of the present disclosure. The method andsystem described herein for providing limited data connectivity can alsobe provided in some embodiments of standalone switches 300. By way of anon-limiting example, a Cisco Catalyst 3K, WS-3850 (commerciallyavailable from Cisco Systems, Inc., 300 East Tasman Drive, San Jose,Calif., 95134, USA), switch may be such a standalone switch 300.

By way of example, the IP phone 142 device is registered on thestandalone switch 300, and a Call Manager system (not depicted) andexternal ports of the IP phone 142 are connected to downlink (i.e.,front panel) ports 305 of the standalone switch 300, then minimaloperation of the reload handler can be invoked when the standaloneswitch 300 goes into reload mode (i.e. ROMmon mode). In such a case, theASIC 310, which in this case may be a Cisco Systems, Inc. ASIC, by wayof example, can maintain its state, and can continue forwarding the dataand control plane traffic without resetting ASIC state and tables.Accordingly, the reload handler 123 releases CPU 340 resources andmaintains the ASIC 310, PHY 320, and PoE controller 330 statesunchanged.

The reload handler 123, upon a crash, reload, or malfunction, adds adefault entry in the ASIC 310 pointing to the CPU 340 into a management(MGMT) port 335 for persistent data interfaces. A minimal slow-pathforwarding module, which is a software module of CPU 340 now startsrunning in the ROMmon/bootloader. A Peripheral Component InterconnectExpress (PCIe) 350, a serial expansion bus standard for connecting acomputer to one or more peripheral devices, or other appropriateinterface, may serve as an interface between the ASIC 310 and theminimal slow-path forwarding module of CPU 340. It is appreciated thatthe slow path is only required if there is no direct connectivity fromthe standalone switch 300 to the call manager from a downlink path(i.e., via downlink ports 305).

All external connectivity from the downlink ports 305 are forwardedthrough regular ASIC forwarding from previously known MAC and IPaddresses. The control path to the MGMT port 335 provides a path to theexternal network 160, and a downstream IP telephone 355.

The minimal operation of the reload handler is invoked.

By way of a summary of the above discussion, a first, dotted line 360indicates “normal” path of data packets through the standalone switch300, and a second, dashed line 370 indicates the path of data packetsthrough the standalone switch 300 when reload handler 123 invokesminimal slow-path forwarding.

Reference is now made to FIG. 4, which is block diagram illustration ofa fourth embodiment, constructed and operative in accordance with anembodiment of the present disclosure. The embodiment depicted in FIG. 4,and described below is similar to the embodiment described above withreference to FIG. 3. A single supervisory module (SUP) 410 isoperatively connected to a standalone modular switch 420. As is known inthe art, modular switches with supervisory modules are typicallydesigned so that control plane management functions, such as, but notnecessarily limited to: Layer 2 and 3 services, redundancy capabilities,configuration management, status monitoring, power and environmentalmanagement, and so forth are controlled by the supervisory module 410.

The supervisory module 410 comprises a plurality of ASICs 430 (depictedas comprising ASICs 430A, 430B, 430C interconnected via the SIF 440).The PCIe 450 serves as an interface between the plurality of ASICs 430and the minimal slow-path forwarding module 460. The minimal slow-pathforwarding module 460 is connected to the outside network 160 via themanagement port 463. A PoE telephone 355 is depicted as the receivingdevice of packets which are sent through the standalone modular switch420 to the supervisory module 410, and to the “outside world” via themanagement port 463 when minimal slow-path forwarding is invoked.

The standalone modular switch 420 is, for the ease of depiction, shownas comprising front panel ports 465, to which is connected the PoEtelephone 142. The standalone modular switch 420 comprises a PoEcontroller 470 and a PHY controller 480, as discussed in earlierembodiments. The standalone modular switch 420 interfaces with thesupervisory module 410 using a stack line interface (SLI) 490.

Aside from the minimal operation of the reload handler, when minimalslow-path forwarding is invoked, the SLI 490 is also maintainedundisturbed in the presently described embodiment.

By way of a summary of the above discussion of FIG. 4, a dotted line 492indicates “normal” path of data packets through the standalone modularswitch 420 and supervisory module 410. A second, dashed line 495indicates the path of data packets through the standalone modular switch420 and supervisory module 410 when reload handler 123 invokes minimalslow-path forwarding.

Reference is now made to FIG. 5, which is a block diagram illustrationof a fifth embodiment, constructed and operative in accordance with anembodiment of the present disclosure. An enterprise modular switch, suchas the modular switch 500, is depicted in a high level manner in FIG. 5.Such switches also offer PoE features. In certain switches, such asmodular switch 500, for example, data switching for the line-cards, suchas LC1 501, LC2, 502, LC3 503, and LC4 504, takes place in thesupervisor module. The line cards comprise an ASIC 526. For ease ofdepiction, the ASIC 526 is only shown in LC1 510. The line-card frontpanel port traffic goes on an aggregated switch link interface (SLI) tothe supervisor module for switching across or even for intra-line-cardswitching. An active supervisor module 510 and a standby supervisormodule 515 comprise the supervisory (SUP) modules of the modular switch500. A network interface (NIF) SLI backplane 530 provides forconnections and interface between the line cards (e.g. LC1 501, LC2,502, LC3 503, and LC4 504) and the supervisor modules 510 and 515.

In order to achieve persistency of data beyond the state and mode to theline cards (LC1 501, LC2, 502, LC3 503, and LC4 504), interfaces to thesupervisor module 510 and 515 forwarding ASIC state also need to bemaintained. Line card power needs to be maintained without interruptionfor persistent PoE and for data. Accordingly, and with reference to FIG.5, the following is performed in order to invoke minimal operation ofthe reload handler:

Line card power is retained.

ASIC 526 state and PCIe (not depicted) interface is maintained from thesupervisory active supervisor module 510 and a standby supervisor module515.

An SLI link state is maintained.

The modular switch 500 maintains its port map as well as the activesupervisor module 510 and a standby supervisor module 515 forwardingtable state is maintained.

Based on port configuration the reload handler 123 of the modular switch500 maintains the PHY and PoE connections to devices which are to bekept active.

Data forwarding for PoE devices is maintained.

Spanning tree and TCP keepalive is disabled.

No new link or PoE device may be added.

By way of a summary of the above discussion of FIG. 5, a first, dottedline 550 indicates “normal” path of data packets through the modularswitch 500 and active supervisor module 510. A second, dashed line 560indicates the path of data packets through the modular switch 500 andthe active supervisor module 510 when reload handler 123 invokes minimalslow-path forwarding.

Reference is now made to FIG. 6, which is a block diagram illustration600 of a generalized embodiment, constructed and operative in accordancewith an embodiment of the present disclosure. FIG. 6 depicts a highlevel discussion of slow path forwarding. Slow path is applicable forthe above scenarios for the cases where the complete stack and/orsupervisor modules in a switch is reloaded. Slow path reflects a worstcase scenario when a host CPU management Ethernet interface (e.g., MGMTport 335 of FIG. 3, to give just one example) is the only available pathto reach the Internet for IP media data or control packet routing.

A software agent 685 runs in the bootloader or ROMmon for handlingpackets to provide a default route to Internet. The software agent needsto modify the source (src) IP address of the packets coming fromEnd-Device (for example, IP telephones 650 and 670) to make itself ananchor for the return path. A mapping of <srcIP, MAC, vlan-id> (i.e.: IPaddress of the source device of the packets; MAC address of the sourcedevice of the packets; and the virtual LAN ID) for downstream packetsflowing to their destination will be needed by the software agent inorder to route the packets to an appropriate device on the access portof switch 660. For example, a packet from IP telephone 650 which isrouted to IP telephone 670 will pass through switch 660, and need toexit switch 660 via the access port of switch 660 which routes thepacket to IP telephone 670. At the time of the reload, an entry will bemade in the ASIC forwarding tables to serve as a look up which willroute to the desired ports. A packet handler will rewrite the packetbefore enqueuing the packet in the outgoing management port driverqueue.

Turning specifically to FIG. 6, various devices are communicating in atypical fashion via the Internet 610. For example, the devices mayinclude a High-performance Computing (HCP) server 620, a call manager630 for IP telephony, a file server, such as a T-FTP (trivial FileTransfer Protocol) server 640, and an IP telephone 650. It isappreciated that these devices are mentioned by way of example only, andmany other devices might be in communication. It is also appreciatedthat “the Internet” 610 is used in an informal fashion, and varioustypes of networks might be involved, said networks comprising servers,routers, switches, and so forth, as is known in the art.

A switch 660 is in communication with IP telephone 670. Upon a crash,the switch 660 enters the bootloader or ROMmon. The switch 660 willinvoke slow path forwarding in accordance with the various embodimentsenumerated above. As described above, the switch 660 will, at a minimummap <srcIP, MAC, vlan-id>, i.e. the path to forward packets from asource device, such as IP telephone 650, to a destination device, suchas IP telephone 670. This mapping is made available to a software agent685, as described above. The software agent 685 will store thisinformation in a table 690 for relevant devices (such as IP telephone670).

Reference is now made to FIG. 7, which is a flow chart of a method ofoperation for an embodiment of the present disclosure. At step 710, aswitch enters bootloader mode. The switch comprises a CPU, such as, byway of example, CPU 122, the CPU comprising a reload handler (forexample reload handler 123), and an ASIC, the ASI comprising ASICforwarding logic.

The reload handler instructs the ASIC to store an ASIC database, theASIC database storing the ASIC forwarding logic (step 720).

The PHY layer state of the switch is maintained by the reload handler(step 730). Use of STP is disabled by the switch (step 740), and the useof TCP keepalive is also disabled in the switch (step 750). At step 760,a hardware state of stack hardware and software comprised in the switchis maintained.

New ports are prevented from becoming active in the switch (step 770).At step 780, the ASIC forwarding logic, in response to the instructionof the reload handler, is stored in the ASIC database by the ASIC.

It is appreciated that software components of the present invention may,if desired, be implemented in ROM (read only memory) form. The softwarecomponents may, generally, be implemented in hardware, if desired, usingconventional techniques. It is further appreciated that the softwarecomponents may be instantiated, for example: as a computer programproduct or on a tangible medium. In some cases, it may be possible toinstantiate the software components as a signal interpretable by anappropriate computer, although such an instantiation may be excluded incertain embodiments of the present invention.

It is appreciated that various features of the invention which are, forclarity, described in the contexts of separate embodiments may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention which are, for brevity, described in thecontext of a single embodiment may also be provided separately or in anysuitable subcombination.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the invention is defined bythe appended claims and equivalents thereof:

What is claimed is:
 1. A system comprising: a central processing unit(CPU) comprised in a switch, the CPU comprising a reload handler; and anapplication-specific integrated circuit (ASIC) comprised in the switch,the ASIC comprising switch forwarding logic, upon the switch enteringbootloader mode, the reload handler being operative to: maintain aphysical layer (PHY) state; instruct the ASIC to store a databasecomprising the ASIC forwarding logic; disable spanning tree protocol(STP) in the switch; disable use of Transmission Control Protocol (TCP)keepalive in the switch; retain a state of stack hardware in switchmemory; and prevent any new ports of the switch from becoming active;and the ASIC being operative to store the ASIC forwarding logic in thedatabase upon receipt of an instruction from the reload handler.
 2. Thesystem according to claim 1 wherein at least one device is connected tothe switch at a downlink, and upon the switch entering bootloader mode,packets received from the device are forwarded by the switch to anuplink.
 3. The system according to claim 2 wherein the at least onedevice comprises a power over Ethernet (PoE) device.
 4. The systemaccording to claim 1 wherein the switch comprises a standalone switch.5. The system according to claim 4 wherein the crash handler isoperative to add a default entry to the ASIC database pointing to amanagement Ethernet port which is to be used for persistent data.
 6. Thesystem according to claim 1 wherein the switch comprises a stackableswitch member switch, and the switch is connected to a master switch ata stack interface.
 7. The system according to claim 6, wherein, upon acomplete stack reload, the crash handler is operative to add an entry inthe ASIC database so that a data-path defaults to a management Ethernetport of the management switch for failed look-ups in the ASIC forwardinglogic of the member switch.
 8. The system according to claim 1 whereinthe first switch enters bootloader mode upon receiving a reload or slotreload command.
 9. The system according to claim 1 wherein the firstswitch enters bootloader mode due to a switch malfunction.
 10. Thesystem according to claim 1 wherein the reload handler is operative tocreate a dynamic destination index upon the switch entering bootloadermode.
 11. The system according to claim 1 wherein the switch is adapted,upon entering bootloader mode, to not provide power to a new power overEthernet (PoE) device.
 12. The system according to claim 1 wherein theswitch is operative, upon the performance of a complete stack reload to:normally forward Open Systems Interconnection (OSI) Layer 2 and Layer 3packets to locations which were previously known; and to punt packetswhich cannot be switched to a next switching level.
 13. A methodcomprising: entering bootloader mode at a switch, the switch comprising;a central processing unit (CPU), the CPU comprising a reload handler;and an application-specific integrated circuit (ASIC), the ASICcomprising ASIC forwarding logic; instructing the ASIC to store an ASICdatabase, by the reload handler, the ASIC database storing the ASICforwarding logic; maintaining, by the reload handler, a physical layer(PHY) state; disabling use of spanning tree protocol (STP) in theswitch; disabling use of Transmission Control Protocol (TCP) keepalivein the switch; retaining a state of stack hardware in switch memory;preventing any new ports of the switch from becoming active; and storingthe ASIC forwarding logic in the ASIC database, by the ASIC.
 14. Themethod according to claim 13 and further comprising, upon the switchentering bootloader mode, forwarding packets received from at least onedevice connected to the switch at a downlink to an uplink.
 15. Themethod according to claim 14 wherein the at least one device comprises apower over Ethernet (PoE) device.
 16. The method according to claim 13wherein the switch comprises a standalone switch.
 17. The methodaccording to claim 16 and further comprising the crash handler adding adefault entry to the ASIC database pointing to a management Ethernetport which is to be used for persistent data.
 18. The method accordingto claim 13 wherein the switch comprises a stackable switch memberswitch, and the switch is connected to a master switch at a stackinterface.
 19. The method according to claim 18 and further comprisingthe crash handler adding an entry in the ASIC database so that adata-path defaults to a management Ethernet port of the managementswitch for failed look-ups in the ASIC forwarding logic of the memberswitch.
 20. An apparatus comprising: means for entering bootloader modeat a switch, the switch comprising; a central processing unit (CPU), theCPU comprising a reload handler; and an application-specific integratedcircuit (ASIC), the ASIC comprising ASIC forwarding logic; means forinstructing the ASIC to store an ASIC database, the ASIC databasestoring the ASIC forwarding logic; means for maintaining a physicallayer (PHY) state; means for disabling use of spanning tree protocol(STP) in the switch; means for disabling use of Transmission ControlProtocol (TCP) keepalive in the switch; means for retaining a state ofstack hardware in switch memory; means for preventing any new ports ofthe switch from becoming active; and means for storing the ASICforwarding logic in the ASIC database, by the ASIC.